The present invention concerns a support disk for a support disk bearing for an open-end spin rotor.
Generic conventional support disks have been disclosed by DE 33 24 129 A1 describing a bearing for spin rotors. The support disks comprise a body, which, for instance, is constructed of plastic or metal and which, on its circumference, possesses a plastic ring that forms the running surface for the rotor shaft that it bears. The plastic ring, in this case, is applied by spraying on to the body. In the present state of the technology, the material used on the circumference of the disk with the plastic ring and which is driven by the shaft is polyurethane polymer.
This elastic plastic ring forming the running surface of the rotor shaft has the characteristic that it possesses damping qualities, so that oscillations may be damped during a vibratory period in the run of the spin rotor. Such vibratory periods can occur, for instance, because of imbalances or through impacts with the driving tangential belts. With the known support disk bearings and support disks equipped with the circumferential surface made of polyurethane, rotational speeds of the rotor shaft of up to 110,00 RPM are possible.
Besides the mentioned advantages, the circumferential polyurethane covering of the support disk also has the drawback of excessive wear. Because of the continual deformation, i.e., compression and expansion of the running surface, this component is heated to such a degree, that complete destruction of the layer occurs. In order to repress this behavior of the support disk, it is a conventional practice within the state of the technology to place a cooling groove in this outer layer. This cooling groove is made known by U.S. Pat. No. 5,178,473.
Along with this breakdown, the known support disks are deficient in that the polyurethane running surface separates itself from the base part of the support disk, whereby destruction of the support disk follows.
In order to avoid problems of this nature, it is a known practice in the state of the technology for such support disks that have the plastic cover layer applied onto the body to provide a form fit connection between the body and the plastic cover layer as seen in a radial direction of the support disk. A support disk of this kind is described in DE 42 27 489 A1. From DE 198 24 286 A1, a support disk has been made known, which is provided with a cleaning groove, as well as a cooling groove. DE 198 24 286 A1 also provides further measures so that, during an operational run of the rotor spinning apparatus, contamination is prevented from getting on the rotor shaft, which would cause additional maintenance.
Experience has shown that the support disks of the state of the technology exhibit faults when installed and, in spite of the known measures, have only a very restricted operational life, which limits their employment in modem rotor spinning machines. The stresses thereby brought about lead to an early failure of the support disks so that, besides the high expenditures for the necessary replacement parts, the productivity of the spinning machine is lessened because of the required maintenance work.
Thus, a principal purpose of the present invention is to eliminate the disadvantages of the state of the technology, and to make available support disks, which provide bearings suitable for open-end spin rotors even at the most extreme speeds of rotation without the detriment of an insufficient length of operational life. Additional objects and advantages of the invention will be set forth in part in the following description or may be obvious from the description, or may be learned through practice of the invention.
This principal purpose of the present invention is achieved through a support disk with a circumferential surface having a cover layer made of rubber.
By means of the formulation of the support disk in accord with the invention, a secure connection is advantageously created between the body and the running surface of the support disk. This connection resists such forces incurred by the in-and-out flexing of the cover layer. Even at the highest speeds of rotation and loadings, the loosening of the applied circumferential layer from the body of the disk does not occur.
Furthermore, the support disk constructed in accord with the invention possesses very good rolling characteristics for the carried rotor shaft. In this way, an unsteady phase in the running behavior of the rotor is substantially ameliorated by the excellent damping properties of the support disk, and vibrations are damped.
The damping operation in the circumferential cover layer of the support disk advantageously can be carried out by the layer without detriment to the quality of the running surface. In particular, the most favorable damping characteristics of the invented cover layer for the running surface of the support disk make it possible to hold the thickness of the cover layer of the support disk to a minimum. This has the additional virtue in that the heat removal from the cover layer is alleviated. The flexing brought about in the cover layer on this account does not lead to excessive heating of the cover layer. This advantage substantially increases the operational life of the cover layer as well as that of the support disk.
In an advantageous development of the invention, the cover layer of the support disk is furnished with a cooling groove for even better dissipation of heat from the cover layer during operation. This cooling groove further increases the wear resistance of the support disk.
Providing a design of the body with circumferential profiling in a radial direction is a favorable design to bring about a form fit connection between the body and the cover layer. Even when this may not seem necessary due to a current application, such profiling does enable future higher load demands to be met by the support disk.
By the design of the cover layer with a cleaning groove for the suppression of contaminant deposits on the rotor shaft, disturbances in operation are reduced. Such deposits are also hindered by the fact that the cover layer of the support disk has a low electrical resistance, advantageously less than 1.0xc3x97109 Ohm. In order to achieve this, the rubber material advantageously is treated with an additive for the increase of its electrical conductivity.
In an advantageous development of the invention, the cover layer on the support disk consists of nitrile rubber ([acrylo]nitrile-butadiene rubber), hereinafter, xe2x80x9cNBRxe2x80x9d.
This material has especially favorable mechanical characteristics, which cause it to be practically abrasion proof in rough operational conditions. Even better advantageous properties are possessed by the rubber H-NBR.
This rubber can contain additives, so that it requires no special aging, which is required, for instance, of the polyurethane used in practice in accord with the state of the technology. NBR or HNBR, as a result of these additives, has the characteristics of an already aged material and thus possesses uniform, unchanging properties from the beginning.
Fortunately, there is found in an advantageous development of the invention, a rubber with a tensile strength to meet at least 28 N/mm2. Advantageously, a rubber is available for use with a Shore Hardness of A 85 to 105. Thereby, favorable damping values can be achieved for the cover layer. Just as advantageous is a rubber with a hardness between Shore D 45 to 70. The use of a rubber for the support disk with an elasticity of at least 29% assures a high resistance to wear and good damping.
If the support disk has one or more grooves on the circumference of the cover layer, then, in an advantageous manner, the support disk cover layer can endure even the highest loadings. The groove can fulfill several purposes. For example, the groove can be used for cooling the cover layer or for the cleaning of the shaft of the open spin rotor. Moreover, by means of the installation of the grooves, the rolling contact friction of the shafts against the support disks is lessened.
If the grooves penetrate to the body of the support disk, that is, if the cover layer is essentially made of a plurality of individual elements, independent of one another, then a highly satisfactory cooling of the cover layer and the support disk is assured. The holding qualities of the rubber of the cover layer onto the body of the support disks, especially when this is made of aluminum, are particularly good. Thus, it is possible to fasten the cover layer without lateral restraint directly to the support disk on the circumferential surface. However, for certain technical manufacturing reasons, certain small lateral restraint may be necessary. The scuffing off of the cover layer from the support disks is not to be feared with the invented formulation of the cover layer within foreseeable loadings.
If the cover layer has a thickness of less than 4 mm or if it is less than 1.9 times the depth of the deepest groove, then the cover layer possesses an especially good relationship in reference to its structural strength and the cooling and cleaning effects of the groove.
Respectively, in accord with each instance, it can be advantageous if one or more cleaning grooves are placed on the cover layer of the support disk.
If the body has been surface treated, especially if the body is of aluminum and has been anodized, then other advantages appear. By means of the surface treatment, damage to the material of the body, particularly by oxidation, is prevented. Besides this, by means of the surface treatment, characterizing colorations are possible, so that the installation of different support disks can be chromatically designated in a simple way and thus unwanted exchanges can be avoided. By means of the special characteristics of the material of the invented cover layer of the support disks, it is even possible to put an anodized surface in place after the installation of the circumferential cover layer. By means of the anodized surfacing, that is, the anodizing of the support disk with the cover layer in place, the circumferential cover layer is not affected and its action is not impaired. The anodizing can take place after the finishing work of the support disk.
Invented support disks with outside diameters between 50 and 80 mm have performed exceptionally well for installation in the support bearing system for spin rotors.
The contact surface between cover layer and rotor shaft shows a width of between 4 and 12 mm. This width is sufficient to see that first, a predominantly slip-free rolling contact of the rotor shaft on the support disk is actuated and, second, the rolling resistance is held to the least possible amount.
For a minimum width of the cover layer, a value of around 2 mm is particularly recommended. At this width, it is even possible to work out a direct fastening of the cover layer on the circumference of the body without lateral restraint between the body and the cover layer. When the body is aluminum, a particularly sufficient hold between the invented cover layer and the circumference is obtained.
Beyond this, the 2 mm is enough to avoid a lateral kinking of the cover layer. In the following, the invention will be described with the aid of illustrative presentations.